That depends on the practical conditions under what you read. As long as you abide by following rules, reading in bed can do little harm to your eyes.
1. Assure plenty of light, better shine from left back.
2. Read with correct posture: keep a distance of 30CM to 40CM between your eyes and the reading.
3. Better read while sitting, instead of lying.
4. Select books printed well with clear letters that easy to read.
5. Take a 5-minute break after every half-hour reading.
If you can get a table beside your bed, it will be better do your reading normally before you go to bed, as bed is mainly for rest as everyone knows.
Of course you cannot read in bed for too long. The main reason is that your body, as well as your eyes are relatively still and you rarely blink when you read something in bed, thus, your eyes will go dry and get damaged from poor light conditions. Therefore, you should try to avoid reading in bed, if you have to do so, you should strengthen the lights. That would benefit your eye health and bones. Anyway, good luck for you.
Well, it is very hard to say that reading in bed is bad for your eye health. Different people have different opinion . As I know, there are many people who are reading book in their bed and even don't care anything about their eyes, but they still have good vision. In other words, it kind of depends on your eye gene. On the other hand, you should also pay more attention to your reading habits. For example, you'd better not read a book in a dark place. Besides, the position and the distance of your reading are also very important, so just be careful about them. So that you can not damage your eyes,
If you read in bed tilting against the back cushion, it is OK. If you are lying in bed when reading, the eye vision may be affected. Your books may obstruct the light source. You may read in dark. Thus, your eyes get the light reflection in the blurry state which have bad influence on your eyes.